When multiple string wells are installed on land, it is relatively simple to provide the option of running the tubing strings either simultaneously or individually, with so-called split tubing hangers being employed when the strings are run individually. For underwater installations, the tendency in the art has been to run the tubing strings simultaneously because of difficulties encountered in remote installation of split hangers. However, running multiple tubing strings simultaneously into a subsea or other underwater well installation requires expensive equipment on the platform or vessel which constitutes the operational base for handling the multiple strings and also presents severe problems in providing blowout preventers which will accommodate two or more tubes without crushing them. Accordingly, much effort has been expended in devising improved equipment for multiple string underwater wells, as seen for example in the following U.S. Pat. Nos.
3,603,401--Nelson et al PA1 3,661,206--Putch et al PA1 3,688,841--Baugh PA1 3,693,714--Baugh PA1 3,741,294--Morrill PA1 3,800,869--Herd et al PA1 3,807,497--Baugh PA1 3,847,215--Herd
Despite extensive prior art effort and considerable success in the field, there has been a continuing need for improved methods and apparatus by which the tubing strings can be run individually into an underwater well, with simple and positive remote orientation of the split hangers, the capability of readily retrieving the hangers individually, fully independent running and retrieval of the tubing strings, improved sealing of the tubing hanger body, improved blowout protection and maximum running clearance at the wellhead for such things as gas lift valves.